Radar systems have been in widespread use since the 1940s, and have continually increased in power and sophistication. In general, a radar arrangement transmits an electromagnetic signal toward a region in which a target may exist, and examines the returned electromagnetic “echo” to determine the presence of a target, its range, andor its bearing. It is well known in the art that the transmitted power must be increased in order to obtain a return signal of a given power from an increased distance. One of the problems which has been associated with radar (and its siblings sonar and lidar) is that of “clutter.” Clutter is simply echoes or returns from objects within the area or region being examined which are irrelevant to the targets of interest. Typical sources of clutter include mountains, trees, buildings, ground vehicles, and other like objects. When targets at long range are to be detected or tracked, the transmitted power must be increased, with the result that clutter objects at greater distances will be revealed, and close-in clutter echo signals become stronger.
Clutter tends to obscure the presence of a target return as viewed on a display. More particularly, receivers are characterized by a finite “dynamic range” over which they operate optimally or linearly. In the presence of clutter, especially of clutter having variable amplitude, a weak target may fall below the dynamic range and become invisible. One early method for reducing the obscuring effects of clutter was “Moving Target Indication,” (MTI) which involved processing of the returned signal or echo so as to tend to suppress those echoes or targets which had constant range and phase, thereby tending to render more visible those targets from objects having a changing range and phase.
Improved methods for clutter control are desired.